Harvesting energy from the environmental vibration sources has received a renewed attention in recent years in part due to their applications in wireless networks and portable electronics.
A number of studies in the literature have investigated utilizing discrete electrical components (DuToit et al., 2005; Adhikari et al., 2009; Renno et al., 2009; Cammarano et al., 2010; Trimble, 2011) or linear control systems (Kong et al., 2010; Cassidy et al., 2011; Trimble, 2011).
In another class of studies, switching electronics are utilized to increase harvested power (Guyomar et al., 2005; Lefeuvre et al., 2006; Makihara et al., 2006). These methods were applied to piezoelectric harvesters to generate a favorable electrical load on the active element and increase the voltage output of the harvester which were also shown to increase the power output.
Switching electrical loads to improve transducer performance has been investigated in various vibration control applications (Jalili, 2002; Liu et al., 2005; Wagg and Neild, 2011). Control of shunt resistance (Clark, 2000) and capacitance (Davis and Lesieutre, 2000) electrically connected across a piezoelectric transducer was shown to improve vibration damping performance of these systems.